diff options
Diffstat (limited to 'flag.go')
| -rw-r--r-- | flag.go | 17 |
1 files changed, 10 insertions, 7 deletions
@@ -24,8 +24,10 @@ functions such as String(), BoolVar(), and Var(), and is therefore unaffected. - Define flags using flag.String(), Bool(), Int(), etc. Example: - var ip *int = flag.Int("flagname", 1234, "help message for flagname") + Define flags using flag.String(), Bool(), Int(), etc. + + This declares an integer flag, -flagname, stored in the pointer ip, with type *int. + var ip = flag.Int("flagname", 1234, "help message for flagname") If you like, you can bind the flag to a variable using the Var() functions. var flagvar int func init() { @@ -42,12 +44,12 @@ Flags may then be used directly. If you're using the flags themselves, they are all pointers; if you bind to variables, they're values. - fmt.Println("ip has value ", *ip); - fmt.Println("flagvar has value ", flagvar); + fmt.Println("ip has value ", *ip) + fmt.Println("flagvar has value ", flagvar) After parsing, the arguments after the flag are available as the slice flag.Args() or individually as flag.Arg(i). - The arguments are indexed from 0 up to flag.NArg(). + The arguments are indexed from 0 through flag.NArg()-1. The pflag package also defines some new functions that are not in flag, that give one-letter shorthands for flags. You can use these by appending @@ -843,8 +845,9 @@ func (f *FlagSet) VarP(value Value, name, shorthand, usage string) { flag := &Flag{name, shorthand, usage, value, value.String()} _, alreadythere := f.formal[name] if alreadythere { - fmt.Fprintf(f.out(), "%s flag redefined: %s\n", f.name, name) - panic("flag redefinition") // Happens only if flags are declared with identical names + msg := fmt.Sprintf("%s flag redefined: %s", f.name, name) + fmt.Fprintln(f.out(), msg) + panic(msg) // Happens only if flags are declared with identical names } if f.formal == nil { f.formal = make(map[string]*Flag) |